Timbuktu Pro was last updated in 2013 and discontinued by Arris a year ago. I have been using it for such a long time, so it is hard to give up and move on. I have been able to make Timbuktu Pro 8.8.5 work under El Capitan by installing it with SIP and Gatekeeper temporarily disabled during installation and configuration. I reenable SIP and Gatekeeper after that, and it just works (until 10.11.4). I always run it in secure mode (over SSH). I just updated El Capitan to version 10.11.4 using the combo updater. Now, Timbuktu Pro no longer receives incoming control connections over SSH. Outbound connections (to Macs running Mavericks or Leopard) still work. I tried uninstalling and reinstalling Timbuktu Pro, but cannot make a connection to control the 10.11.4 Mac. Maybe OS X is blocking the connection, or Timbuktu cannot bind to SSH, or the Timbuktu Host process is not running or not listening. I am still searching for a reliable fix. There must be a few people left who still use Timbuktu Pro. Has anybody found a way to make Timbuktu Pro work reliably as a host for incoming control connections?